Keratoconus Differential Diagnoses

Updated: Oct 17, 2018
  • Author: Karen K Yeung, OD, FAAO; Chief Editor: Hampton Roy, Sr, MD  more...
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DDx

Diagnostic Considerations

Keratoconus should be differentiated from other causes of corneal steepening and irregular oblique astigmatism, imprecise variable subjective refractions, and non-inflammatory central corneal scarring. These may include corneal surgery, healed infections, and trauma.

Stromal striations similar to Vogt striae occur when corneas swell (rather than thin) from either hypoxia (associated with wear of contact lenses) or with early Fuchs corneal dystrophy.

Iron depositions in the basal epithelium (similar to a Fleischer ring) can occur in any area of relative depression in the corneal surface (eg, in association with pterygium, surgical scars, and central depressions from refractive surgery).

Pellucid marginal degeneration is often considered a variant of keratoconus. In pellucid marginal degeneration, corneal thinning occurs about 1 mm above the inferior limbus, resulting in advanced against-the-rule corneal astigmatism that may be observed on corneal topography or tomography.

Terrien marginal corneal degeneration is a mildly inflammatory disease, usually of the superior limbus. This disease can also induce irregular against-the-rule astigmatism and corneal thinning (often with vascularization and lipid deposits).

Keratoglobus is an extremely rare corneal disease in which the entire cornea, from limbus to limbus, thins, sometimes to the point where spontaneous perforation becomes possible. Keratoglobus is probably unrelated to keratoconus.

Posterior keratoconus is another extremely rare disease (or nonexistent), in which the posterior corneal surface suffers a loss of substance. This condition is probably unrelated to keratoconus.

Posterior polymorphous corneal dystrophy can lead to keratoconic-like steep cornea. [21]

Differential Diagnoses